Previously, the limit during a single transaction was 10. We've removed this limit and added a cumulative cross-namespace limit.
There’s now no limit on the number of certified namespaces that can be invoked in a single transaction. However, the number of operations that can be performed in each namespace must not exceed the per-transaction limits. In place of the former limit, there’s a new limit on the cumulative number of operations that can be made across namespaces in a transaction. This cumulative limit is 11 times the per-namespace limit. For example, if the per-namespace limit for SOQL queries is 100, a single transaction can perform up to 1,100 SOQL queries. In this case, the cumulative limit is 11 times the per-namespace limit of 100. These queries can be performed across an unlimited number of namespaces, as long as any one namespace doesn't have more than 100 queries.
The new cross-namespace limit applies to the per-namespace limits listed in Execution Governors and Limits.